It was just one letter of thousands the Prime Minister's wife receives every year. Julie Oakley told the story of her 15-year-old daughter and how her life had been blighted by school bullying. Death threats, physical abuse and insults left Emma so low she took an overdose and nearly died.

Oakley, a mother from a small town in south Gloucestershire, is revealed today as the person who left Cherie Booth so angry she agreed to that rare occurrence - a move into the public arena.

Writing in today's Observer, Booth reveals her disappointment with the way many schools deal with bullying. She says too often teachers claim it is not a problem, despite Government policies to tackle the issue.

'Last week I received a letter from the mother of a teenage girl,' Booth says, referring to Emma. 'Her 15-year-old daughter was the sort of girl we might all feel proud to be the parent of. She didn't smoke, drink, go out late and was motivated and hard working at school.

'But her mum wanted my help. The girl had recently tried to commit suicide. Why? Because she was being bullied at school to such an extent that she felt worthless enough to want to take her own life and was too scared to tell her parents until it was almost too late.'

Tomorrow, Booth will chair a conference on bullying organised by the charity Childline. The conference will hear that for the fifth year running bullying has been the major problem among the 20,000 calls received by the charity. 'In some schools sadly there is still a tendency to claim "It doesn't happen here", or to adopt an approach which forces the problem underground rather than out in the open,' Booth says.

'[That is] in spite of a government requirement on them to adopt strategies to minimise bullying. It is surely not acceptable for parents to feel they have no alternative to move schools to escape, which happens in all too many cases. That is a victory for the bully.

'Bullying will not stop if it is tolerated or ignored. We have to be reminded bullying doesn't have to be an inevitable part of school life.'

Oakley was delighted to have had had such an effect on the woman some describe as the deputy Prime Minister. 'I have sent letters to a lot of celebrities,' Oakley said. 'I just hoped that the Prime Minister's wife would be able to help.'

Like many parents, Emma's parents at first missed signs their daughter was being bullied. Emma was staying away from school, was argumentative and withdrawing into herself. It was not until she broke down that her parents realised the torment she was suffering.

'You feel like you have let them down,' she said. 'As a parent you are supposed to protect your children. We knew there was something wrong but didn't know what it was.'

Emma, whose name has been changed to protect her identity, was put under pressure by friends to take drugs. When she refused she was called names, was pushed and shoved around the playground and suffered from the latest form of bullying, text messaging. A message sent to her mobile phone said: 'Aren't you on the slab yet?' meaning dead.

The full extent of Emma's problems dawned on her parents when, last spring, friends found the teenager collapsed on the street outside her home.

'She was brought back in a car by a friend, she looked terrible, she couldn't speak,' her mother said. 'I thought at first it was drugs but then I had an instinct that she had tried to kill herself.'

Emma was taken to hospital where she stayed for three days. Doctors discovered she had taken over the preceding 72 hours, 41 paracetamol and 15 prescription painkillers called Tylex. When Emma arrived home her mother slept in the same bed as her daughter for a week to comfort her and keep an eye on her. 'I didn't sleep a wink,' Oakley said.

They then went to the school where the reaction was the one many parents complain of, and Booth raises in her article - complacency.

'They wanted to brush it under the carpet,' said Oakley, who has now started her own self-help group, Bullywatch. 'They are worried they will get a bad name, but I would think more of a school if they were honest and said they would tackle the problem head-on.'